The present disclosure relates to video coding and, in particular, to video coding techniques that apply to video having low motion content.
Many modern electronic devices support exchange of video between them. In many applications, a first device captures video locally by an electronic camera and processes the captured video for transmission to another device via a bandwidth-limited channel. The video typically has a predetermined frame size and frame rate which does not change during the video exchange process. Several coding protocols have been defined to support video compression and decompression operations. They include, for example, the ITU H.263, H.264 and H.265 standards.
The inventors foresee that video exchange may expand to include exchange of video generated by other techniques, such as video generated by a user interface of a device or video generated by an application program. In a simple example, a user at a first terminal may desire simply to exchange contents of his device's display with another user. A video coding system, therefore, may be called to code contents of a workspace on the device's display and transmit the coded data to another device. Doing so raises unique challenges that are not adequately handled by traditional coding protocols.
Traditional coding protocols involve lossy compression techniques. The process of coding video data and decoding it includes errors which means that decoded video data generated by a decoding device will resemble the source video from which it was generated but with some distortion. When coding “natural” video (e.g., video captured by a camera), such distortions are not always perceptible due to movement in image content or other factors. When coding computer-generated content, however, particularly low motion content, such distortions likely will be more perceptible because the content and, therefore, the distortions are displayed to a viewer for a prolonged period of time.
The problems of compression losses increase for higher resolution content. When coding natural content that possesses motion, a human viewer may perceive coding at one resolution (say, 720p) to be of sufficiently high quality. When coding synthetic content that has low motion, however, the same viewers may perceive coding at that same resolution to be low quality, again, because codding errors and distortion become more evident. Viewers may require decoded video data to be of a higher resolution, perhaps 1080p or 4K resolution, to maintain sufficient quality.
Accordingly, the inventors perceive a need in the art for coding techniques that process low motion content in video with high precision. The inventors further perceive a need in the art for coding techniques that recognize when low motion content is present in video and adapt processing techniques to increase precision and improve coding quality.